What is Modern Physics?
PhysicsModern designates the new conceptions of Physics developed during the first three decades of the 20th century, which resulted from the theoretical propositions of physicists Albert Einstein and Max Planck. After the emergence of ttheory of relativity of Einstein and the quantizationof electromagnetic waves, this new field of study emerged, expanding the limited horizons of Classical Physics.
More comprehensive than the Physicsclassic, The Modern physics is able to explain phenomena of scales much small (atomic and subatomic) and very high speeds, very close to the speed of light. the physicists of the century XX realized that current knowledge was not enough to explain phenomena such as photoelectric effect Or the blackbody radiation. Thus, several hypotheses began to be raised about the naturegiveslight and of the matter and about the interaction between them.
Important Discoveries of Modern Physics
Several experiments marked the history and development of Modern Physics. Among them, we can mention those who have given us a deeper understanding of the structure of matter and atoms and also the nature of light. check out some examples of these important discoveries that marked the beginning of Modern Physics:
In 1895, Wilhem Rontgen discovered the existence of X-rays, an invisible type of extremely penetrating radiation.
In 1896, Antoinebecquerel discovered the existence of radioactivity.
A few years later, in 1900, the German physicist MaxPlanck proposed that the energy carried by the electromagnetic field had values quantized, multiples whole of a minimal and constant quantity.
In 1905, through his theory of relativity, AlbertEinstein he showed that frames that move with speeds muchtall,next à velocity propagation giveslight, experience the passage of time and the measurement of distances in different ways.
In 1913, NielsBohr proposed that the energy levels of electrons scattered around atomic nuclei are quantized, that is, its energy is given by an integer multiple of a minimum value.
In 1924, the dualitywave-particle, established by the physicist LouisDe'Broglie, showed that any body can behave like a wave.
In 1926, the mechanicsQuantum, result of the work of physicists as WernerHeisenberg and Erwin Schrödinger.
In other words, the PhysicsModern managed to explore the nature of worldmicroscopic and the big ones speedsrelativistic, providing valuable explanations for several physical phenomena that were, until then, misunderstood.
Landmarks of Modern Physics
→ Atomistic theory
THE theoryatomistic originated among Greek thinkers as talesinMiletus and the atomists Democritus and Leucipus. For these thinkers, matter was made up of smaller, indestructible and indivisible particles, which were called atoms.
Atomistic theory gained strength thanks to the different atomic models proposed throughout physical studies. See below some important scientists and their atomic theories:
JohnDalton: he believed that atoms were massive and indivisible and that substances were formed by atomic combinations of different proportions.
J. J. Thomson: according to this scientist, the electrons, which have a negative electrical charge, were scattered on the surface of a positive charge.
ErnestRutherford: for Rutherford, atoms had a positive electrical charge concentrated in an extremely dense and reduced region called the atomic nucleus.
NielsBohr: according to the Bohr model, electrons were located around atomic nuclei with energy quantized, that is, they only occupied specific levels of energy, which were multiples of a smaller.
See too: Atomic models
The current conception of what atoms are has had several contributions throughout history, undergoing several changes. Some of the most important proposals for our understanding of atoms and matter came from physicists such as De'Broglie,Heisenberg and Schrodinger. Check out:
Louis De'Broglie: proposed the existence of matter waves, a property that explains the dual behavior of electrons.
WernerHeinsenberg: proposed the principle of uncertainty, indicating that it would not be possible to determine, simultaneously and with complete precision, the position and amount of movement of quantum particles.
ErwinSchrodinger: through his equation, he was able to determine the regions most likely to find an electron around the atomic nucleus.
Lookalso:The birth of Quantum Mechanics
→ Black body radiation
For Physics, it is classified as bodyblack any body capable of absorbing all the radiation incident on it, re-emitting it in the form of thermal radiation, according to its temperature.
The problem of blackbody radiation was one of the main open questions in physics at the beginning of the 20th century. Through the hypothesis of quantizing the energy of electromagnetic waves emitted by black bodies, the German physicist Max Planck presented the solution to this problem.
→ Oil drop experiment
O oil drop experiment, performed by the physicist RobertAndrewsMillikan, was able to determine the order of magnitude of the electrical charge of the electrons. The apparatus used in this experiment consisted of a spray bottle, which sprayed oil droplets between two plates arranged electrically charged in the vertical direction, so that the droplets were static on the air. Until this experiment was carried out, the charge of the electrons was not known, only the ratio between their charge and yours pasta.
Lookalso: The discovery of the electron
→ Franck-Hertz Experiment
O experimentinFranck-Hertz validated the atomic model proposed by NielsBohr. This experiment showed that it is only possible to excite the atoms of a gas from levelsspecific of energy, as well as the quantization of energy levels, proposed by Bohr.
→ Rutherford Experiment
The famous Rutherford experiment was actually performed by two of his students, Hansgeiger and ErnestMardsen. In this experiment, a thin gold leaf was bombarded by particlesalpha (Helium atomic nuclei) at high speed. It was noticed that, after the collision, the angles of some of these particles varied greatly. Also, in some cases, there were ricochet of alpha particles, which suggested the existence of heavy and extremely dense atomic nuclei.
→ Discovery of gravitational lenses
The phenomenon of lensgravitational it occurs due to the distortion of space-time exerted by large masses, such as those of stars and planets. According to general relativity, proposed by AlbertEinstein, the gravity exerted by massive bodies is the result of the deformation in the relief of space-time. As a result, when propagating through the deformed space-time, the light would undergo a deviation.
This phenomenon was observed by astronomers by measuring the duration of the total solar eclipse that occurred in 1919. Measurements were carried out simultaneously in the city of Sobral, located in the state of Ceará, is on They areThomas and Prince.
Lookalso: Einstein and Ceará
→ Michelson-Morley experiment
the experiment of Michelson-Morley proved that electromagnetic waves are capable of propagating in a vacuum itself, so they don't need a medium to do so. To prove this property, the researchers AlbertMichelson and EdwardMorley used a large interferometer (device used to investigate light interference) dipped in a pool filled with Mercury. In this way, vibrations of any kind, capable of affecting the extremely sensitive measurement, would be avoided.
In the experiment in question, the time for light to be reflected by precisely aligned mirrors was measured. If the Earth moves in the medium in which light propagates, small deviations in the reflected beams should be observed, which did not occur. Thus, the researchers proved the proposed theory.
→ Photoelectric effect
O It is madephotoelectric it was a phenomenon without a satisfactory explanation until the studies developed by AlbertEinstein. By being able to explain this effect, Einstein was awarded a NobelinPhysics. Through the idea of MaxPlanck, Albert Einstein extended the theory of energy quantization from blackbody radiation to any type of radiation, thus establishing the notion of wave-particle duality.
general relativity
THE relativitygeneral is a generalization of the special theory of relativity, also developed by the German physicist Albert Einstein. According to this theory, massive bodies, such as planets and stars, are capable of deforming the fabric, or relief, of space-time. This deformation, in turn, gives rise to gravity.
The gravity of stars and planets deforms space-time, giving rise to gravity.
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*Image credits: Benjamin Couprie, Institut International de Physique de Solvay / Wikimedia Commons.
By Me. Rafael Helerbrock